What hardware do I need?

I have 2 projects but could do with understanding hardware requirements.

Project 1

Libelium open aquaponics shield over Arduino uno sensing pH, conductivity, and temperature + tank level using ultrasonic distance sensor + pump run time.

Want to average readings for pH, conductivity + temperature over a 5 minute period then compare previous period and only POST data to a server via GPRS when there is a change.

HARDWARE THOUGHTS: Either Arduino Uno + RPi & GSM dongle or Arduino Yun & GSM shield

Project 2

POST Temperature, tank level and pump run time every 4 - 6 hours irrespective of status change or not.

HARDWARE THOUGHTS - Arduino Uno + GSM shield for prototypes then hopefully spark electron when it arrives October for final versions.

Both projects will be hard wired so no battery requirements.

The question is - do I really need to manage data transfer if all I want to do is send a 5 or 10 minute average of pH, conductivity, temperature, tank level and run time? Will a simple timed GET request suffice and use a smoothing function to maintain a constant stream average. This would be the best scenario as it simplifies hardware.

Many thanks

I don't really understand your question. It seems to me that neither project places a heavy demad on the Arduino so I would be tempted to choose the cheapest solution.

Are you talking about two separate projects, or do you want to choose hardware that can be swapped from one to the other?

...R

One hardware solution that I can swap would be ideal.

I am trying to establish in principle what is the baseline system I require to achieve my goal. Would an arduino uno with gsm shield suffice for both instances? Would an SD card shield be useful?

I'm confused: isn't GPRS General Packet Radio System, which is totally different to GSM Global System Mobile? They do a similar job but the hardware at both ends is completely different.

You say you want to post this to a server? What kind of server? Where is the server? If it's a PC in your house, then I would attach it directly to the server with USB or possibly Ethernet. If it's a server in a service provider farm somewhere then Ethernet or GSM. Have you already tested GSM messaging to this server?

The SD card is useful if you want to take lots of readings while the PC is turned off and then manually copy the data off the card while the data logger is turned off.